1. The Field of the Invention
The present invention is directed to systems, apparatus, and methods for remediating explosives. More particularly, the present invention is directed to the remediation of explosives which have not detonated.
2. Background Art
Explosive charges are inherently dangerous in a number of respects. Inadvertent detonation poses risks of severe personal injury or death, as well as of substantial property destruction and consequential losses. Explosive charges are, in addition, comprised of material substances, which, even when not consolidated in a shape capable of performing as a detonatable explosive charge, may be toxic and thus potentially injurious to human health and to complex as well as simple plant and animal life.
Explosive charges that are not securely stored in a supervised manner, or isolated from the environment and from indiscriminate access by human and animal life forms, thus present both safety and environmental hazards.
Such hazards are pointedly apparent where an explosive charge fails to detonate after the explosive charge has been installed for that purpose during activities pertaining to mining, construction, or to seismic surveying. Fortunately, installed explosive charges that do not detonate as planned are usually locatable and often recoverable through the expenditure of reasonable efforts and without safety risks to personnel. On the other hand, there do routinely arise circumstances in which undetonated explosive charges of this type are not recovered or simply cannot be recovered. In such circumstances, there exists a risk that the undetonated explosive charge could at some subsequent time be detonated inadvertently or become a source of potentially harmful contaminants.
As an example, seismic survey data used to ascertain the nature of subsurface ground structures is routinely obtained by recording and analyzing shock waves that are propagated into the ground and produced by detonating explosive charges. The shock waves are then monitored dining transmission through the ground. In this role, such seismic charges are usually utilized in large sets, installed as an array of individual seismic charges at widely dispersed locations. The seismic charges are interconnected with detonation equipment for remote detonation, either simultaneously or in sequence.
Seismic charges for such surveys can be detonated either above or below the surface of the ground. In either case, it is not uncommon that at least one of any set of such seismic charges does not detonate as intended. Such failures may be caused by defects in the explosive charge itself, by damage caused during installation, by faulty detonation equipment, or by the failure of personnel in the field to make effective interconnections between that detonation equipment and each seismic charge in the installed set.
When a seismic charge installed above the ground fails to detonate as intended, it is usually possible to locate and safely recover the undetonated seismic charge. Nonetheless, circumstances do exist where the detonation of a set of seismic charges installed above the ground dislocates one of the undetonated seismic charges in the set, directing that undetonated seismic charge into a terrain in which the charge cannot be located or cannot be recovered easily. Responsible seismic crews naturally are trained to exercise all reasonable efforts to recover undetonated seismic charges that are located on the surface of the ground, but even the most rigorously indoctrinated and enthusiastic seismic personnel cannot guarantee that all undetonated seismic charges installed above the ground are ultimately recovered.
Aside from the human factor involved, the intervention of severe weather conditions, such as sandstorms, blizzards, tornadoes, or hurricanes, can impede efforts to recover undetonated seismic explosives. Some such weather conditions offer the prospect of even altering the terrain, thereby burying the undetonated seismic charge temporarily or for a substantial duration. Floods can cover the seismic survey site, removing or obscuring undetonated seismic charges. In the extreme, geological surface changes, such as mudslides, rockfalls, and fissures caused by earthquakes, by heavy weather, or even by seismic survey activity itself, can preclude the recovery of undetonated seismic charges, and even obscure the understanding that any seismic charge has failed to detonate.
The safety risks and environmental hazards posed by loose, undetonated explosive charges will be present where any undetonated seismic charge remains unrecovered after the detonation of the set of seismic charges of which it was a part.
The likelihood that an undetonated seismic charge will be abandoned is greatest, however, relative to the conduct of seismic survey activity based on the detonation of seismic charges installed below the surface of the ground. In such sub-surface seismic detonation activity, a series of deep boreholes is drilled into the earth or rock at predetermined locations that are intended to maximize the data to be derived from the shock waves promulgated from the detonation of the seismic charges. A seismic charge is placed at the bottom of each borehole and then shut in the borehole in a relatively permanent manner using a concrete or a sealing compound, such as bentonite. The balance of the borehole is then backfilled with loose soil and rock, a process which alone accounts for the majority of failed seismic detonations. Backfill materials have an understandable tendency to break the detonating cord leg wires or non-electric transmission line that interconnects the installed seismic charge at the bottom of the borehole with detonating equipment located above the ground. If a seismic charge installed below the ground fails to detonate, the easy removal of the undetonated seismic charge is seriously impeded by yards of backfill and the cured concrete or sealing compound in which the seismic charge was embedded at the bottom of the original borehole. Removing such an installed seismic charge by reexcavating the original borehole or by digging around the original borehole to avoid the sealing compound is extremely laborious and time consuming, potentially unsafe, and in many circumstances virtually impossible.
Thus, in conducting seismic survey activities, particularly seismic survey activities involving the detonation of seismic charges below the surface of the ground, undetonated seismic charges are regularly abandoned in the field. Frequently, even the precise location of undetonated seismic charges cannot be pinpointed. The risks from undetonated explosive charges installed in the ground endure for a substantial time, usually exceeding the durability of ground surface warning signs, fencing, or the continued possession and control of access to the site by an original owner. Eventually, the pressure of human population growth may render the site attractive for civil or industrial activities that would not be consistent with buried undetonated explosive charges.
The associated dangers include first that of an accidental detonation at some future time. Less dramatic, but certainly of longer duration, are risks presented by the material substance of those undetonated charges. Once released from the confines of the casing of an explosive assembly, the explosive material therein may cease to present any risk of explosion. This type of release of explosive materials can occur through corrosion of the casing through the action of ground water, the fracture of the casing during careless installation, or the shifting of the ground structure at the location at which the undetonated seismic charge was abandoned. In due course, the prolonged effect of these forces in combination with surface erosion or subsurface fluid migration can disperse over a large area the material of a fractured explosive charge. That material may constitute a potentially problematic contaminant. Even if detected, remedial activities may be required to contain and possibly eliminate the contaminant.
Nonetheless, no practical methods exist for reliably remediating the risks posed by undetonated explosive charges, particularly where those undetonated explosive charges are originally installed below the surface of the ground.